Clean benches have often been used as a device for improving the air cleanliness in a local work area. A conventional clean bench has a work opening only on the front side of the work table and is enclosed on the other sides for maintaining cleanliness. Such a clean bench is provided with a purified air discharge port within the enclosure and the worker inserts his hands from the front work opening to do tasks.
However, the work opening of a clean bench is small and causes a problem with the workability when the worker assembles precise machines or does other tasks. Furthermore, where products or manufacturing parts are moving as on a manufacturing line, a traditional measure is to enclose the entire line in a clean room; then, a problem is that the equipment becomes large.
For the above reason, a local cleaning apparatus has been proposed (Patent Literature 1) in which a pair of push hoods (purified air discharge devices) capable of discharging a uniform purified air flow is placed with their air flow opening surfaces facing each other so that the air flows from their respective air flow opening surfaces collide with each other and create a purified air space having a higher level of cleanliness in the area between the pair of push hoods than in the other areas.